Operation of a cylindrical bioelectrochemical reactor containing carbon fiber fabric for efficient methane fermentation from thickened sewage sludge

A bioelectrochemical reactor (BER) containing carbon fiber fabric (CFF) (BER + CFF) enabled efficient methane fermentation from thickened sewage sludge. A cylindrical BER + CFF was proposed and scaled-up to a volume of 4.0-L. Thickened sewage sludge was treated using three types of methanogenic reactors. The working electrode potential in the BER + CFF was regulated at −0.8 V (vs. Ag/AgCl). BER + CFF showed gas production of 3.57 L L−1 day−1 at a hydraulic retention time (HRT) of 4.0 days; however, non-BER + CFF showed a lower gas production rate (0.83 L L−1 day−1) at this HRT, suggesting positive effects of electrochemical regulation. A stirred tank reactor (without CFF) deteriorated at an HRT of 10 days, suggesting positive effects of CFF. 16S rRNA gene analysis showed that the BER + CFF included 3 kinds of hydrogenotrophic methanogens and 1 aceticlastic methanogen. These results demonstrate the effectiveness of the BER + CFF for scale-up and flexibility of this technology.